In an image forming apparatus which forms an image on a sheet by discharging ink to the sheet with an inkjet head, a paper jam may occur during transportation of the sheet by a sheet transportation portion. In such an image forming apparatus, an ink discharge surface is provided on a lower surface of the inkjet head. The ink discharge surface has a large number of ink discharging nozzle openings for discharging the ink. The sheet transporting portion (i.e., a paper transport belt) is provided below the ink discharge surface at a small space interval. A user may insert his/her hand or the like in the vicinity of the inkjet head in order to rectify the paper jam occurring in the vicinity of the inkjet head. If a user's hand or the like touches the ink discharge surface of the inkjet head, it is likely to break meniscuses of the ink within the ink discharging nozzles which are open in the ink discharge surface. The meniscus as used herein is a surface on which the ink in the nozzles comes into contact with the open air. The state of the meniscus has an influence on the flying state of the ink. In the case where the meniscus is broken, a satisfactory discharge of the ink cannot be achieved and printing quality is deteriorated. Specifically, the hand or the like comes into contact with the nozzles of the inkjet head resulting in contaminants or the like entering the nozzles, or the ink within the nozzles soiling a hand or the like. In some cases, the meniscuses may be broken or at least damaged.
JP 2005-96187 relates to a conventionally proposed technology of covering the ink discharge surface with a sheet-like shutter in order to prevent, when paper jam occurs, a user from coming into direct contact with the ink discharge surface. For example, the direct contact can occur when a user inserts his/her hand in the vicinity of the inkjet head. With this technology, the user's hand will not be in contact with the ink discharge surface, thereby producing a high-quality image formation on a sheet.
However, in the image fowling apparatus described above, if the sheet remains attached to the ink discharge surface during paper jam, the sheet is caught in the shutter when the shutter moves to a position where the shutter faces the ink discharge surface. Therefore there is a likelihood that the ink discharge surface cannot be protected by the shutter. In such a scenario where the ink discharge surface is not protected, if the user touches the ink discharge surface with a hand, the hand may be stained with the ink. In addition, the meniscuses within the ink discharge nozzles may be broken and/or damaged and lead to the deterioration of printing quality. Moreover, there may be cases where the removal of the paper jam takes a long period of time. For instance, if the ink discharge surface is left unprotected for a period of time, i.e., 30 minutes or more under a state where the air is dry, there is a fear that the ink in the nozzles may dry and the nozzles will be clogged. Alternatively, there is also a fear that the ink in the nozzles will dry, which will cause increased viscosity of the ink and in turn cause defective discharge.